Are flat rooflights secure?

Security only matters where someone can get to the glass, so start by being honest about height. A rooflight on a two-storey loft conversion is above the reach of anyone without a ladder and is rarely worth losing sleep over. The ones that deserve thought are the low, flat ones: a lantern or a run of rooflights over a single-storey rear kitchen extension, a flat garage roof, or an outrigger you can step onto from a bay window, a garden wall, a wheelie bin or a boundary fence.

On a flat roof the glazing sits close to horizontal, which changes the geometry of a break-in. Someone standing on the roof is above the glass and can put their weight straight down onto it, rather than levering sideways at a vertical window. That is the scenario a secure specification has to answer, and it is answered mostly by the glass itself.

There are two kinds of safety glass and the difference matters here. Toughened glass is heat-treated so it shatters into small blunt pebbles instead of shards. It is strong under an even load, but once it does break it is gone in one go and leaves a clear opening. Laminated glass is two sheets bonded around a plastic interlayer. Hit it and the outer sheet can crack, but the interlayer holds the fragments in place, so you cannot knock a hole through it quietly and you cannot clear the opening with a couple of blows.

For a reachable flat rooflight the specification that does the work is a sealed double-glazed unit with a toughened outer pane and a laminated inner pane. The laminate is the barrier a person has to defeat, and defeating it is loud, slow and awkward, which is the opposite of what an opportunist wants. There is a useful overlap with the regulations too. Overhead glazing has to be safety glass under Part K anyway, to stop anyone falling through it, and a laminated inner pane is a common way of meeting that, so the secure option is often only a small step up from what the roof needs regardless.

If you want the enhanced level, ask whether the unit is tested to PAS 24, the security standard used for windows and doors. A rooflight built to PAS 24 has been through a set of manual attack tests as a complete assembly, glass, frame and locking together, rather than just carrying a strong pane in an ordinary frame.

A fixed rooflight has no handle, no hinge and no mechanism to force, and the glass is bonded into the frame at the factory, so on pure security it is the strongest option. Where the glass is glazed from the inside, the beads that hold the pane cannot be prised off from the roof, which closes off the other obvious line of attack. Good non-opening units are built this way as standard.

Opening units are where the detail counts, because now there is a joint that has to resist being levered. What you are looking for is a multi-point locking mechanism or shootbolts that engage the frame in several places, not a single central catch. Electric opening rooflights help here, because a well-made one has no external handle at all and the actuator holds the sash shut and locked when it is closed, so there is nothing on the outside to grip or turn. If you want the detail on those, our page on electric skylight installation sets it out. On any opening unit, ask how many locking points it has and whether the hinges are concealed or exposed on the outer face.

Not every flat rooflight is glass. Polycarbonate and acrylic domes are cheaper and lighter, and polycarbonate in particular is very hard to smash, which sounds like a security advantage. The weakness is usually not the material but how the dome is fixed. Older domes clip or screw down through an exposed upstand, and a fixing you can reach from the roof is a fixing that can be undone or levered. Thin acrylic can also be cut.

For a reachable opening on a house, a glass unit with a laminated inner pane and internal glazing is the more secure choice, and it is quieter to defeat than most people assume the other way round. Polycarbonate earns its place on garages, outbuildings and budget-led work, and if that is your situation the trade-offs are covered on our plastic and polycarbonate skylight installation page. Judge it on how it is held down, not just on how tough the sheet is.

When you are specifying a flat rooflight you can reach, ask for four things: a laminated inner pane, internal glazing so the beads are not accessible from outside, a multi-point lock on any opening unit, and, if you want the tested level, a unit rated to PAS 24. Get the glass specification sheet rather than a spoken assurance, because “safety glass” and “toughened” are not the same as laminated, and only the sheet tells you which pane is which.

There is a neat overlap worth knowing about on a south-facing extension. Those rooflights already want solar-control glass to keep the room below from overheating in summer, which is the reason we specify orientation and G-value before anything else. The solar-control coating goes on the outer pane and the laminate goes on the inner, so you can have both the summer comfort and the security in one unit without compromising either. That is a common brief on the rear-extension work covered by our flat roof skylight installation service.

If you would like us to specify the whole unit rather than just the hole in the roof, tell us how the extension is reached and roughly how big the opening is, and we will come back with a glass and locking specification and a price. Ring 01702 898232 or request a quote.